Understanding Food Webs

Overview

In this second lesson of Exploring Ecosystems Together, students build on their understanding of simple food chains. They investigate how several connected food chains form a food web and collaboratively represent feeding relationships in a local ecosystem.

Learning intentions

• WALT explain how food chains can connect to form a food web.
• WALT identify producers, consumers and decomposers in an ecosystem.
• WALT use arrows to show the direction of energy flow.
• WALT work collaboratively to represent relationships between organisms.

Success criteria

• I can explain that plants are producers and form the beginning of food chains.
• I can identify what different organisms eat and connect them accurately.
• I can draw arrows from the food to the organism that eats it.
• I can explain that a food web shows several connected food chains.

Curriculum links

• Biological Science — Relationships in an ecosystem: representing relationships in ecosystems using food webs.
• Biological Science — Food chains: identifying nutritional relationships between plants and animals using basic food chains.
• Science capabilities: interpreting and representing information, communicating explanations, and participating and contributing.
• Key competencies: thinking; relating to others; managing self; participating and contributing.

Lesson structure (45 minutes)

1. 0–5 min · Reconnect and hook. Open with the hook and food-chain recap slides and display a grassland image containing grass, insects, mice, birds, frogs, snakes, hawks and decomposers. Ask, “What might happen if the grass disappeared?” Students discuss with a partner, then recall a simple food chain from the previous lesson. Collect a few examples and clarify that arrows show energy moving from the food to the eater.

2. 5–12 min · Direct teach. Use the food-web teaching slides to model how two or more food chains can share organisms. Build a small example on the board, such as grass → grasshopper → frog → hawk and grass → mouse → hawk. Explain that the connected chains form a food web, that plants are producers, and that animals are consumers. Briefly include decomposers as organisms that break down dead material and return nutrients to the ecosystem. Students identify the producer, consumers and decomposer, and practise saying what each arrow means.

3. 12–17 min · Check understanding. Display the questions on the guided-check slides: “What does the arrow point towards?”, “Why can one organism have several arrows pointing to it?”, and “Would a food web usually have one chain only?” Students show their answers on mini-whiteboards or fingers, then explain one answer to a partner. Address the common misconception that arrows show “who eats whom” without representing energy flow; restate that the arrow points to the eater.

4. 17–32 min · Collaborative construction. Arrange students in six groups of five and give each group a section of poster paper, markers and a set of organism cards from the Food Web Interaction Cards. Groups choose a shared ecosystem context, such as grassland, forest, pond or coastal habitat, then position relevant organisms and connect them with arrows. They must include at least one producer, several consumers and a decomposer, and check that every arrow shows energy moving from food to eater. Circulate, asking: “What does this organism eat?”, “Could it have more than one food source?”, and “How does your web connect more than one chain?” Students record a short explanation beside their web.

5. 32–40 min · Gallery critique and improve. Use the gallery-walk and feedback slides to show the review prompts: “Is there a clear producer?”, “Do arrows point in the direction of energy flow?”, “Are several food chains connected?”, and “Is the decomposer included or explained?” Groups rotate to view two other posters and leave one specific warm comment and one question or suggestion. Groups return to their poster, discuss the feedback and make one improvement.

6. 40–45 min · Plenary and exit check. Return to the plenary slides and ask students to complete the food-web explanation sheet independently. They draw or describe one connection between two food chains and answer: “How is a food web different from a food chain?” Invite two students to share. Collect the worksheet as an exit check and preview that the next lesson will explore what may happen when one population changes.

Resources

• the complete food-web slide deck
• the food-web explanation sheet
• the Food Web Interaction Cards
• Six large sheets of poster paper
• Coloured markers
• Blu-tack or tape
• Mini-whiteboards or scrap paper
• Copies of the organism cards
• Access to a board or display

Assessment

• Listen during partner talk and questioning for accurate use of producer, consumer, decomposer, food chain and food web.
• Check group posters for connected chains, appropriate organisms and correctly directed arrows; use the gallery prompts to identify misconceptions.
• Use the completed worksheet to assess whether students can explain the difference between a food chain and a food web and represent energy flow accurately.

Differentiation

• Provide a partially completed example, a word bank and sentence starters such as “The ___ is a producer because…” and “The arrow points to ___ because it eats ___.”
• Pair students strategically and assign group roles: card organiser, illustrator, arrow checker, explanation writer and discussion leader.
• Support EAL learners with the picture-based cards, gestures, repeated oral rehearsal and opportunities to explain ideas in a home language before sharing in English.
• For students needing additional support, limit the web to five or six organisms and provide a teacher-selected ecosystem. Challenge confident students to include an organism with more than one food source and explain how removing one population could affect two others.